APPENDIX B Hydrological Assessment COWAL GOLD OPERATIONS PROCESSING RATE MODIFICATION Environmental Assessment 2018 REPORT Cowal Gold Operations Processing Rate Modification Surface Water Assessment Prepared for: Evolution Mining (Cowal) Pty Limited Revision Description Author Reviewer Approved Date b Second Draft TSM Resource Strategies TSM 1 Feb 2018 c Rev b comments removed TSM TSM 7 Feb 2018 d Revised following client review TSM Evolution Mining TSM 21 Feb 2018 e Revised IWL pump rate for oxide processing TSM TSM 8 Mar 2018 f Revised with minor edits TSM Resource Strategies TSM 20 Mar 2018 g Revised: added detail for future development TSM Resource Strategies TSM 22 Mar 2018 h Revised following client review TSM Evolution Mining TSM 27 Mar 2018 TABLE OF CONTENTS 1.0 INTRODUCTION ................................................................................................................... 1 1.1 EXISTING MINE AND MODIFICATION DESCRIPTION ....................................................... 1 1.2 ASSESSMENT REQUIREMENTS ........................................................................................ 3 1.3 SUMMARY OF RELEVANT FINDINGS OF PREVIOUS ENVIRONMENTAL APPROVALS DOCUMENTATION .............................................................................................................. 6 2.0 HYDROMETEOROLOGICAL SETTING ................................................................................ 8 2.1 REGIONAL HYDROLOGY .................................................................................................... 8 2.2 METEOROLOGY .................................................................................................................. 8 2.3 WATER QUALITY ............................................................................................................... 11 2.3.1 Lake Cowal ................................................................................................................. 11 2.3.2 Other Water Quality Monitoring ................................................................................... 19 2.4 HARVESTABLE RIGHT ...................................................................................................... 19 2.5 GROUNDWATER ............................................................................................................... 19 3.0 CURRENT CGO WATER MANAGEMENT AND WATER SUPPLY ..................................... 20 3.1 DESCRIPTION ................................................................................................................... 20 3.2 CONTAINED WATER STORAGES .................................................................................... 23 3.3 PIT DEWATERING ............................................................................................................. 23 3.4 WASTE ROCK EMPLACEMENT WATER MANAGEMENT ................................................ 24 3.5 TAILINGS STORAGE FACILITY WATER MANAGEMENT ................................................. 24 4.0 FUTURE CGO WATER MANAGEMENT AND WATER SUPPLY ........................................ 25 4.1 WATER MANAGEMENT .................................................................................................... 25 4.1.1 Staged Future Development ........................................................................................ 25 4.1.2 Integrated Waste Landform ......................................................................................... 30 4.1.3 Reconstructed Up-Catchment Diversion System ......................................................... 31 4.2 WATER SUPPLY ................................................................................................................ 32 4.2.1 General ....................................................................................................................... 32 4.2.2 Saline Groundwater Supply Bores ............................................................................... 35 4.2.3 Eastern Saline Borefield .............................................................................................. 35 4.2.4 Bland Creek Palaeochannel Borefield ......................................................................... 35 4.2.5 Lachlan River .............................................................................................................. 35 5.0 SIMULATED PERFORMANCE OF WATER MANAGEMENT SYSTEM ............................... 37 5.1 MODEL DESCRIPTION ...................................................................................................... 37 5.1.1 General ....................................................................................................................... 37 5.1.2 Climatic Data ............................................................................................................... 38 5.1.3 Runoff Simulation ........................................................................................................ 40 J1006-10.r1h.docx Page i TABLE OF CONTENTS (Continued) 5.1.4 Groundwater Inflow and Borefield Supplies ................................................................. 40 5.1.5 CGO Water Demands ................................................................................................. 41 5.1.6 IWL Initial Reclaim Water Losses ................................................................................ 42 5.2 SIMULATED FUTURE PERFORMANCE............................................................................ 43 5.2.1 Overall Water Balance ................................................................................................. 43 5.2.2 CGO External Water Demand ..................................................................................... 44 5.2.3 Maximum Pit Water Volume ........................................................................................ 46 5.3 CLIMATE CHANGE EFFECTS AND WATER BALANCE IMPLICATIONS .......................... 46 5.4 INTERACTION WITH LAKE COWAL .................................................................................. 47 6.0 POST-CLOSURE WATER MANAGEMENT SYSTEM ......................................................... 49 6.1 EIS POST-CLOSURE MANAGEMENT CONCEPTS .......................................................... 49 6.1.1 Waste Rock Emplacements ......................................................................................... 49 6.1.2 Tailings Storages ......................................................................................................... 49 6.1.3 Final Void .................................................................................................................... 49 6.2 MODIFICATION POST-CLOSURE WATER MANAGEMENT ............................................. 50 6.2.1 Final Void Water Balance ............................................................................................ 50 6.2.2 Implications of Climate Change on Final Void Water Balance ..................................... 51 7.0 POTENTIAL SURFACE WATER IMPACTS AND MITIGATION MEASURES ...................... 52 7.1 OPERATIONAL PHASE ..................................................................................................... 52 7.2 POST-CLOSURE ................................................................................................................ 52 8.0 REFERENCES .................................................................................................................... 54 LIST OF TABLES TABLE 1 RAINFALL DATA SUMMARY 10 TABLE 2 EVAPORATION DATA SUMMARY 10 TABLE 3 SUMMARY OF LAKE COWAL WATER QUALITY – GENERIC PARAMETERS 12 TABLE 4 SUMMARY OF LAKE COWAL WATER QUALITY – METALS 13 TABLE 5 SUMMARY OF EXISTING/APPROVED INTERNAL CATCHMENTS AND CONTAINED WATER STORAGES 23 TABLE 6 PROPOSED CGO ORE PROCESSING RATES 32 TABLE 7 ANNUAL CGO LACHLAN RIVER EXTRACTION VOLUMES 36 TABLE 8 MODELLED PUMP RATES 38 TABLE 9 SEASONAL EVAPORATION PAN FACTORS 39 TABLE 10 WATER BALANCE MODEL AWBM PARAMETERS 40 TABLE 11 IWL INITIAL WATER BLEED WATER REDUCTIONS 42 TABLE 12 WATER BALANCE MODEL RESULTS (AVERAGED OVER REMAINING MINE LIFE ML/YEAR) 44 J1006-10.r1h.docx Page ii LIST OF FIGURES FIGURE 1 REGIONAL LOCATION 2 FIGURE 2 EXISTING ENVIRONMENTAL MONITORING LOCATIONS 9 FIGURE 3 FIELD MEASUREMENT OF PH AT SELECTED SITES – LAKE COWAL 15 FIGURE 4 FIELD MEASUREMENTS OF PH – LAKE COWAL 16 FIGURE 5 RECORDED COPPER CONCENTRATIONS AT SELECTED SITES – LAKE COWAL 16 FIGURE 6 RECORDED LEAD CONCENTRATIONS AT SELECTED SITES – LAKE COWAL 17 FIGURE 7 RECORDED ZINC CONCENTRATIONS AT SELECTED SITES – LAKE COWAL 17 FIGURE 8 FIELD MEASUREMENTS OF TURBIDITY AT SELECTED SITES – LAKE COWAL 18 FIGURE 9 RECORDED TOTAL PHOSPHOROUS CONCENTRATIONS AT SELECTED LAKE SITES AND LAKE WATER LEVEL 18 FIGURE 10 MODIFICATION GENERAL ARRANGEMENT 21 FIGURE 11 CGO WATER MANAGEMENT SYSTEM SCHEMATIC 22 FIGURE 12 CONCEPTUAL GENERAL ARRANGEMENT YEAR 16 (2020) 26 FIGURE 13 CONCEPTUAL GENERAL ARRANGEMENT YEAR 20 (2024) 27 FIGURE 14 CONCEPTUAL GENERAL ARRANGEMENT YEAR 26 (2030) 28 FIGURE 15 CONCEPTUAL GENERAL ARRANGEMENT POST-MINING 29 FIGURE 16 EASTERN PUMP STATION 34 FIGURE 17 MONTHLY RAINFALL COMPARISON – CGO METEOROLOGICAL STATION AND DATA DRILL 39 FIGURE 18 PREDICTED OPEN PIT GROUNDWATER INFLOW RATE 41 FIGURE 19 AVERAGE MODELLED SYSTEM INFLOWS AND OUTFLOWS 43 FIGURE 20 PREDICTED ANNUAL EASTERN SALINE BOREFIELD USAGE 45 FIGURE 21 PREDICTED ANNUAL BLAND CREEK PALAEOCHANNEL BOREFIELD USAGE 45 FIGURE 22 PREDICTED ANNUAL DEMAND FROM LACHLAN RIVER ENTITLEMENTS 46 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